Conventionally, generally, a coated tool produced by forming a hard coating layer, which is constituted by (a) as a lower layer and (b) as an upper layer on the surface of a body (hereinafter, referred to as a “cermet body”) formed of a titanium carbonitride (hereinafter, referred to as TiCN)-based cermet is well known. (a) The lower layer is a Ti compound layer which includes two or more layers of a Ti carbide (hereinafter, referred to as TiC) layer, a Ti nitride (hereinafter, referred to as TiN) layer, a Ti carbonitride (hereinafter, referred to as TiCN) layer, a Ti oxycarbide (hereinafter, referred to as TiCO) layer, and a Ti oxycarbonitride (hereinafter, referred to as TiCNO) layer, each of which is formed through chemical vapor deposition, and has an average total layer thickness of 3 to 20 μm; and (b) the upper layer is an aluminum oxide (hereinafter, referred to as Al2O3) layer which is formed through chemical vapor deposition and has an average layer thickness of 1 to 25 μm.
Although the coated tool in the related art has relatively excellent wear resistance, abnormal wear such as chipping is likely to occur therein under cutting work conditions in which a high load is exerted on a cutting edge. Therefore, various proposals for the structure of the hard coating layer have been made.
For example, Patent Document 1 discloses a method of producing a coating cermet in which a titanium nitride layer is chemically deposited on the surface of a cermet including 70 to 95 wt % of a hard dispersed phase-forming component of one type or two or more types of carbides, nitrides, and carbonitrides of Ti, Zr, Hf, Ta, Nb, W, Mo, and Cr and 5 to 30 wt % of a binder phase-forming component of one or two or more of Co, Ni, and Al. In the method of producing a coating cermet, a method of producing a coating cermet by forming the titanium nitride layer through chemical vapor deposition on the surface of the cermet at a temperature of 700° C. to 900° C. using a mixed gas of titanium tetrachloride, ammonia, and hydrogen is proposed. It is thought that a coating cermet which has high wear resistance and can be used for a longer period of time than in the related art can be accordingly provided.
In addition, Patent Document 2 discloses a surface-coated titanium carbonitride-based cermet cutting tool produced by forming a hard coating layer including a plurality of layers formed of two or more of a Ti carbide, a Ti nitride, a Ti carbonitride, and an aluminum oxide on the surface of a titanium carbonitride-based cermet body containing 12 to 20 wt % of a binder phase-forming component primarily containing Co and Ni, using a chemical vapor deposition method or a physical vapor deposition method. Regarding the surface-coated titanium carbonitride-based cermet cutting tool, a configuration in which the surface portion of the body is formed as a binder phase layer having an average layer thickness of 0.5 to 1.5 μm and containing a binder phase constituent component, and the hard coating layer that comes into contact with the binder phase layer of the surface portion of the body is formed as a binder phase constituent component diffusion prevention layer having an average layer thickness of 0.5 to 5 μm and containing titanium nitride is proposed. It is thought that excellent toughness is accordingly exhibited.
In addition, Patent Document 3 discloses a cutting tool insert made of a carbonitride alloy containing Ti as a primary component and containing W and Co, which includes a wear-resistant layer formed by a chemical vapor deposition method of one layer or a plurality of layers formed of carbides, nitrides, oxides, or borides (excluding borides of the element B) of the elements Ti, Al, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si, or B, a combination thereof, or a solid solution thereof, and is coated to have a total coating thickness of 1 to 20 μm. Furthermore, Patent Document 3 proposes a cutting tool insert made of a carbonitride alloy containing Ti as a primary component and containing W and Co, in which the coating layer does not have cooling cracks, the wear-resistant layer formed of a single layer or a plurality of layers having the same crystal structure and having a thickness of greater than 1 μm by a chemical vapor deposition method has a compressive residual stress of 200 to 500 MPa at room temperature; the carbonitride alloy containing Ti as a primary component and containing W and Co is formed of C, N, Ti, W, and Co, the atomic fractions of the elements satisfy the relationships of 0.25<N/(C+N)<0.5, 0.05<W/(W+Ti)<0.11, and 0.09<Co<0.14; Ti is partially substituted with Ta, Nb, V, Zr, Hf, and/or Mo, the amount of each element is less than 5 at %, and the total amount of the elements is less than 10 at %. In the above-described configuration, it is thought that the cutting tool insert made of a carbonitride alloy exhibits excellent toughness and wear resistance.